This invention relates to apparatus for surgical excision of tissue, and more particularly to such apparatus that employs a snare wire energized with ultrasound to grasp, cut, and coagulate the tissue.
In the practice of surgery, it is well known to employ a wire loop, or snare, to encircle a tissue to be cut. The wire is energized with electricity that enables the tissue to be coagulated as it is being cut. This stops the bleeding. The procedure is commonly applied for surgical excision of the tonsils. It is also employed through an endoscope to remove polyps from the intestine. In this case the snare assembly must be very long, greater than 150 centimeters. A problem encountered with this technique is that the coagulation or electrocautery action is not very localized. It occasionally happens that the adjacent intestinal tissue is injured enough to cause perforation of the intestinal wall with serious consequences. In many surgical applications, electrocautery is being replaced by ultrasound cutting and cauterizing. In this case a sharp rigid blade is vibrated at ultrasound frequencies and applied to a surface to be cut. The blade vibrates the tissue surface, cutting and coagulating the tissue as it advances to prevent bleeding. Because the action is localized to the tissue directly in contact with the blade, there is no spread of damage to adjacent tissue.
U.S. Pat. No. 5,989,264 issued Nov. 23, 1999 to Wright discloses an ultrasonic polyp snare designed to grasp, cut and coagulate polyps in the intestine through a flexible endoscope. A rigid blade at the distal end of an elongate flexible waveguide is excited by an ultrasonic transducer at the proximal end of the waveguide. A snare wire affixed to the distal end of the blade extends past the blade and along the waveguide to its proximal end. The blade and wire are maneuvered to surround the polyp at its base. This may be difficult when the polyp has a mushroom shape, because the blade is rigid. The snare wire must then be greatly enlarged to fit over the large polyp head. The apparatus may not be easily passed through the tortuous path that the endoscope may follow in certain intestines, because the blade is rigid. Surgeons developed great skill in manipulating a snare wire at the end of the catheter. The manipulation required by the Wright device with the snare on the side of the blade would require further training. It will not be as easily mastered.
It is accordingly an object of the invention to provide an ultrasonically vibrating snare wire at the end of an elongate flexible waveguide that can grasp, cut, and coagulate tissue. It is another object that the snare be operable at the end of an endoscope that is inserted into the intestines. It is yet another object that the snare be operable in a manner similar to an electrocautery snare to facilitate operator usage. The flexible ultrasonic surgical snare of the invention comprises an elongate flexible tubular sheath. A flexible waveguide having proximal and distal ends extends through the sheath. Ultrasonic vibrations are applied to the proximal end of the waveguide. The distal end of the waveguide is ultrasonically coupled to a wire loop or snare. The snare can be extended beyond the sheath to encircle a polyp, and then retracted into the sheath by operation of the proximal ends of the sheath and/or waveguide while the snare is vibrated at ultrasonic frequency to cut and coagulate the polyp. In operation, an endoscope is passed into the intestine. When polyps are found, the snare is passed through the endoscope and the snare extended to encircle the polyp. With the snare vibrating, the snare is retracted into the sheath to cut off and coagulate the polyp. In a first embodiment of the invention, both legs of the loop are affixed to the distal end of the waveguide, and the loop is retracted by retraction of the waveguide relative to the sheath. In a second embodiment of the invention, one leg of the loop is affixed to the distal end of the waveguide, and the second leg of the loop extends in an elongate wire back to the proximal end of the sheath, and the loop is retracted by pulling on the proximal end of the extended leg.
These and other objects, features, and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings in which like elements are designated by like reference characters in the various drawing figures.